I just had a real good experience in having some tracks mastered with Kevin Nix who works out of LNix Mastering, Ltd. at Ardent Studios in Memphis, TN, USA.
L. Nix Mastering, Inc. - Main Page (website)
MySpace.com - L. NIX MASTERING - MEMPHIS, Tennessee - Rock / Hip Hop / Blues -
MySpace.com - L. NIX MASTERING - MEMPHIS, Tennessee - Rock / Hip Hop / Blues - www.myspace.com/lnixmastering (myspace)
It was really easy to get the tracks to him and back via the internet. The turnaround was fast. The price was unbelievably cheap ($45 a track). Most important, the results were professional. The tracks came with a lot of clarity and definition, including some soulful "Memphis bottom."
If you are looking for a no hassles mastering process, Kevin is definitely worth a look.
http://web.mac.com/mwm711